Semiconductor devices including fast recovery diodes (“FREDs”) are well-known and are a hybrid of Schottky diodes and P-N junction diodes. This arrangement produces a lower forward voltage drop at higher currents, along with a higher switching speed than is available in only a P-N junction diode or a Schottky diode. It is desirable when switching from current passing mode (when a semiconductor device is forward biased) back to current blocking mode (when the semiconductor device is reverse biased) that the required reverse voltage can be achieved quickly and that this voltage remains stable once achieved.
It is important for fast recovery diodes to have a stable reverse bias breakdown voltage (reverse bias breakdown voltage is also sometimes referred to as blocking voltage) to ensure the performance and reliability of the semiconductor device. Unfortunately, some fast recovery diodes, especially those being used in relatively high voltage applications (e.g., about 500 V or greater (e.g., about 500 V to about 2000 V)), can have reverse bias breakdown voltages that can change or become unstable, for example, when the diode is exposed to moisture (e.g. high humidity conditions for example greater than about 60% relative humidity) and/or when trace amounts of ionic contamination (e.g., sodium or the like) are present on the surface layer of the diode or the like semiconductor structure. In particular, when a negative voltage bias is applied, for example, to the main anode of some fast recovery diodes in the presence of high humidity, dormant surface charges on the exterior of the diode can become mobile and pool together to create localized pockets of electric fields in undesirable locations that can alter the depletion zones of the dopant tubs or wells of the diode, causing a reduction (e.g., “walk-in” effect), for example, in the reverse bias breakdown voltage, thereby detrimentally affecting the performance and reliability of the semiconductor device. Additionally, in some cases when the device is not packaged and/or is not in a controlled low humidity environment, the degrading effect of moisture on the reverse bias breakdown voltage can be more severe. Therefore, the testing conditions for the device should be considered when determining the magnitude of these effects on the device.
Accordingly, it is desirable to provide semiconductor devices including semiconductor structures such as fast recovery diodes or the like that have a stable reverse bias breakdown voltage, for example, even in the presence of moisture, to improve the performance and reliability of the semiconductor device and methods for fabricating such semiconductor devices. Furthermore, other desirable features and characteristics will become apparent from the subsequent detailed description and the appended claims, taken in conjunction with the accompanying drawings and this background.